In heat exchangers made from multiple, stacked, tubes or plate pairs defining flow passages therein, it is common to use turbulizers located in the tubes or between the plates inside the plate pairs to enhance heat transfer, especially where a liquid, such as oil, passes through these flow passages. These turbulizers are commonly in the form of expanded metal inserts and they have undulations or convolutions formed therein to create turbulence in the flow and in this way increase heat transfer in the heat exchanger.
While conventional turbulizers do increase heat transfer, a difficulty with these turbulizers is that they also increase flow resistance or pressure drop inside the heat exchanger. In fact, the flow resistance increases even more than the heat transfer gain produced by the turbulizer, because only a part of the increased turbulence caused by the turbulizer is effective in promoting heat transfer. The balance is wasted in inefficient eddies or vortices.
The present invention periodically interrupts the convolutions in the turbulizer to form non-convoluted pressure recovery zones located between the convolutions. Surprisingly, this substantially reduces the pressure drop caused by the turbulizer without appreciably reducing heat transfer.